The present invention relates to atomizers and, in particular, to atomizers of the type which include a gas exit, at least one outlet in the region of the gas exit and a deflector for deflecting gas issuing from the gas exit across the at least one outlet whereby a substance to be atomized is drawn out of the at least one outlet and atomized. These atomizers atomize liquids or powders into the gas.
Most conventional atomizers of the above type operate continuously whether atomization is required or not. Strictly speaking, when such atomizers, frequently called nebulisers, are used in medical applications, atomization is only required during the inhalation phase of a breathing cycle so that a drug can be administered by deposition in the lungs. In practice a patient usually inhales for about 30 percent of the breathing cycle, consequently, use of a continuously operating atomizer results in a large proportion of the atomized drug being wasted.
Some designs of medical atomizer overcome such wastage by giving the patient a trigger to start the atomization when they begin to inhale. Such a trigger controlled type of atomizer is not satisfactory since the patient must coordinate inhalation with trigger operation.
In one conventional atomizer a gas duct leads gas under pressure to a gas exit, a reservoir for holding the substance to be atomized is formed around the base of the gas duct, and a sleeve placed around the gas duct defines a passageway through which the substance to be atomized may pass to at least one outlet. A fixed deflector in the form of a bar is disposed in line with the gas outlet so that gas issuing from the gas exit is defected so as to pass over the outlet or outlets. The passage of gas over each outlet draws the substance to be atomised from the reservoir, through the passageway to each outlet. The deflected gas atomizes the substance, and atomized particles of the substance are carried away during the inhalation phase of the patient since the patient breathes air or gas in through the atomizer some of the drug is lost while the patient is not inhaling.
Atomizers are used in other applications. For example, powders or liquid may be sprayed from a jet, the liquid or powder being atomized and entrained by a propellant. In conventional sprays, operation is controlled by a valve for releasing propellant. When the valve is released, the spraying operation is stopped and some of the liquid or powder collects in the jet since insufficient propellant has been released. The collected spray either dries to block the jet or is propelled by a re-started spraying operation in large droplets. Where paint is being sprayed, this causes splatter and uneven deposition on a surface to be painted.
It is an object of this invention to reduce at least some of the above disadvantages of the above-mentioned prior art.
The present invention is defined in the appended claims.